Author(s): FLEISCHMANN, C., SINDIANI, M., KORMAN, M., Institution: ARIEL UNIVERSITY, Country: ISRAEL, Abstract-ID: 505

INTRODUCTION:
Ramadan fasting, observed annually by close to 2 billion Muslims worldwide, requires abstinence from eating and drinking from dawn to sunset for a whole lunar month. This form of religious diurnal intermittent dry fasting creates distinct metabolic and physiological challenges, particularly regarding fluid homeostasis. While physical activity during Ramadan has been studied, relationships between objectively measured daily activity and homeostatic regulation of hunger, thirst, and hydration remain inadequately characterized.
METHODS:
In the spring of 2021–2023 (March-May), 287 Ramadan-observing Muslim participants and 76 culturally and ethnically matched controls residing in Israel participated in the study (mean age 26±7 years, 59% female). At five time points (one week pre-Ramadan, Ramadan weeks 1 and 4, and weeks 1 and 4 post-Ramadan), the participants reported physical activity frequency (no. of 30-min. sessions per week). A subset of 230 participants (63.4%) using wearable devices reported average daily step counts (mean 10,450±5,481 steps/day; range 1,000-25,000). Mixed linear models examined associations between both activity measures and hunger, thirst, absolute hydration (L/day), relative hydration (mL/kg/day), and appetite timing, adjusting for age, gender, and BMI.
RESULTS:
Self-reported activity showed no associations with homeostatic outcomes in Muslims but predicted higher hydration in controls (absolute: F=6.63, p=0.011; relative: F=4.87, p=0.029). Objectively measured step counts predicted hydration in both Muslims (relative: F=16.69, p<0.001; absolute: F=16.97, p<0.001) and controls (p<0.05), with each additional 1,000 steps associated with ~1.4% higher relative hydration in Muslims. Step counts showed no consistent associations with hunger, thirst, or appetite timing. An exception emerged at Ramadan week 1, where Ramadan-observing Muslims with higher step counts reported lower hunger (p=0.028). In the controls, higher self-reported physical activity was associated with higher hunger at Ramadan week 4 (p=0.035).
CONCLUSION:
Objective activity measurement revealed selective homeostatic associations during Ramadan. Daily step counts consistently predicted fluid regulation in both groups yet showed minimal association with subjective sensations (hunger, thirst, appetite timing). This dissociation suggests physical activity influences fluid and appetite homeostasis through distinct regulatory pathways, prioritizing fluid balance maintenance during fasting. An exception occurred during early fasting adaptation (week 1), when Muslims with higher step counts reported lower hunger (p=0.028), a fasting-specific pattern not observed in controls, who showed higher hunger with increased self-reported physical activity at week 4 (p=0.035). The failure of self-reported activity to capture step-count effects underscores the need for objective behavioural measurement in Ramadan research.